It is known to equip a winch with a security apparatus comprising a toothed wheel, wedged on the shaft of the winch, a worm meshing with the toothed wheel, a housing slidingly receiving the worm, a motor, termed “follow-up motor,” making it possible to rotate the worm so that it follows the rotation of the toothed wheel during normal operation of the winch, and means for damping the sliding of the worm in the housing in the case of an exceptional failure situation of the winch. This security apparatus, known under the “Motosuiveur” mark, is described in document No. EP 1 253 102.
In a normal operating situation of the winch, the worm is in a normal position bearing against said damping means, and the follow-up motor rotates the worm at a speed adapted to that of the toothed wheel, which in turn is rotated by the winch; the security apparatus is then inactive or “transparent,” i.e. it does not interfere with the operation of the winch.
In the event the winch fails, the shaft thereof undergoes an immediate acceleration generated by the weight of the load, which is transmitted to the toothed wheel of the security apparatus, and which the worm cannot follow; this results in sliding of the worm in the housing, from its aforementioned normal position toward an exceptional position stressing said damping means then, when the damping capacities of said damping means are reached, up to a stop position.
In one embodiment, these damping means comprise a piston, against which the worm bears, nozzles with a reduced section, through which the piston forces oil in which the worm soaks, elastic washers situated between the ends of the worm, and the stop formed by the housing. Such damping means are described in document No. U.S. Pat. No. 7,331,252.
The aforementioned security apparatus makes it possible to monitor said exceptional failure situation by blocking the load against falling.
At the end of that blocking, it is necessary to regain control of the load so as to release the winch, which involves accessing the security apparatus so as to rotate the worm manually, since the follow-up motor is not powerful enough to rotate the worm (this is not its role).
However, in a certain number of situations, said access is not possible or is restricted, for example when the winch is used in the nuclear industry. Furthermore, manually actuating the worm is a tedious operation, the pitch of the worm being relatively small and the diameter of the toothed wheel being relatively large.
The present invention aims to resolve these significant practical drawbacks.
Another exceptional situation exists in which the operation of the winch is stopped, i.e. when a brake comprised by the winch tightens until it locks the shaft of the winch, for example in the event of an electrical power loss. It is then no longer possible to regain control of the load easily and quickly, i.e. without a manual intervention on the security apparatus or the winch.
The present invention also aims to resolve this gap.